The present invention relates to a new and improved construction of a chair support or chair frame structure.
In its more specific aspects, the present invention relates to a new and improved construction of a chair support or chair frame structure equipped with a seat holder or support and a backrest holder or support. The seat holder or support is inclinably or reclinably connected at the front end thereof where the seat user's knees will fit with a supporting or support structure by means of a first swivel or pivot joint possessing a substantially horizontal axis of rotation and is inclinably or reclinably connected at the backrest end of such seat holder or support with the backrest holder or support by means of a second swivel or pivot joint possessing a substantially horizontal axis of rotation. The backrest holder or support possesses an arm or arm structure extending from the second swivel or pivot joint towards the supporting structure and which arm or arm structure is pivoted or swivelably connected at the supporting structure by means of a third swivel or pivot joint possessing a substantially horizontal axis of rotation. At the backrest holder or support there acts a spring or resilient element supported at the supporting structure, and the supporting structure is supported at a foot support or foot frame unit by means of a second spring or resilient element.
Chairs, whose chair support or frame structure is constructed with a backwardly-inclinable seat holder and a backrest holder, are known from various prior art constructions. In the simplest known exemplary form, one end of both the seat holder and the backrest holder is swivelably or hingeably connected in spaced relationship from a supporting structure about a respective horizontal axis or shaft, whereby the seat holder or part is connected at its other end with the backrest holder by means of a swivel or pivot joint. When the seat holder or part is tilted backwards, the backrest holder tilts as well as the seat holder or part, and for this purpose one of the swivel or pivot joints is additionally constructed as a sliding joint or else an extra or supplementary connecting link or bracket is positioned at one of the swivel or pivot joints.
In order to increase the seating comfort, it is known, for example, from my commonly assigned U.S. Pat. No. 4,502,729, granted Mar. 5, 1985, and entitled "Chair, Especially a Reclining Chair", to position a height-adjustable backrest at the backrest holder or carrier, which is moved downwards by an amount corresponding to or in functional relationship to the backwards or rearward inclination of the seat holder or carrier.
In order to arrange this displaceable or slidable backrest in a functionally satisfactory manner, it is necessary to construct the backrest holder or carrier as a double support or column. However, this entails a greatly increased expenditure of materials which results in correspondingly greater costs.